Labradorite

Labradorite is a type of feldspar consisting of between 30-50% Albite and 50-70% Anorthite.

It is grey to grey-black with colourful iridescence, or spectral "labradorescence" caused by diffraction of light in the layers of rock. This causes the stone to flash sheens of various blues or greens, or a a whole spectrum of colours, when held at different angles.

It is named after Labrador in Canada, where it was first found in 1770. It has since been found in other places, including Finland, Madagascar, and Australia.